In September 1943, under the cover of darkness, six British midget submarines crept into the heart of enemy territory, penetrating a heavily guarded Norwegian fjord in an attempt to eliminate the threat of the powerful German battleship, the Tirpitz. Numerous previous attempts to attack the ship from both air and sea had failed, and this mission was carefully strategized, and undertaken by skilled operatives who had undergone extensive training in an isolated sea loch. Though five of the six X-Craft submarines were either lost or captured, two crews had just enough time to lay their explosive charges, which detonated after they were forced to the surface, putting the Tirpitz out of action for a crucial six-month period. Masterminded from a top-secret naval headquarters on the east coast of Scotland, Operation Source has been memorialised as one of the most daring naval raids of World War II. This new study tells the complete story of this epic operation in unparalleled detail, supported by full-colour illustrations and contemporary photography.